Fabrication of slag surfaces and structures



g- 3 1968 G. WELTY ET AL 3,396,641

FABRICATION 0F SLAG SURFACES AND STRUCTURES Filed Dec.

AC1 w m .n m 1 u @QL W5 QJ N w v 0M [S United States Patent 3,396,641FABRICATION 0F SLAG SURFACES AND STRUCTURES Lloyd G. Welty, 132 S. LaskyDrive, Beverly Hills, Calif. 90212, and Simon J. Sluter, 5523 RimpauBlvd., Los Angeles, Calif. 90043, assignors of one-half each to Weltyand Sluter Filed Dec. 16, 1964, Ser. No. 418,840 3 Claims. (Cl. 9422)Our present invention relates, in general, to the fabrication ofcomposite trafiic bearing surfaces and other structures employed for avariety of utilitarian purposes, and having properties conducive tosafety in service. More particularly, our invention relates to thefabrication of such structures from slag.

It is already known to fabricate composite surfaces and structures forsomewhat similar purposes from other materials. For example, US. Patent2,925,831 utilizes a fragmented cinderlike material of volcanic originfor such fabrication.

It has now been found that slag, hitherto thought to be merely aworthless waste product in a metal smelting process, can be used in thefabrication of surfaces and structures with resultant unique featuresand improvements over existing compositions as will be described indetail hereinafter.

Subsequent to reclamation the slag is preferably reduced to theappropriate size for use by conventional grinding, rolling and screeningmethods.

Spectrographic analyses of typical slag and scoria specimen are asfollows:

It will be appreciated that the indicated materials will be combinedwith oxygen and other components to form the various chemical compoundsof the minerals.

As employed herein, slag is defined as the dross which is obtained as aproduct of smelting a metal from an ore containing silicates andgenerally with a lower specific gravity than the metallic substancesextracted. For example, slag may be produced in a smelting operation inwhich fluxing agents such as limestone and fluorite are intermixed witha siliceous ore, e.g., of iron which mixture is then fused as in a blastfurnace. The slag as dross forms a fluid layer overlying matter smeltedmetal wherefrom it is poured off and cooled. The cooled material is thenfragmented and sized as described above.

As may be noted slag differs quite markedly from volcanic scoria inchemical composition. The slag granules also differ in being of theorder of twice the density of the scoria and has a compressive strengthand abrasion resistance of upwards of twice to three times that ofscoria. Slag and scoria possess individually distinctive surfacecharacteristics and structure together with other differences notedelsewhere herein provide compositions of correspondingly differentcharacteristics which are particularly advantageous under differentconditions of use. Moreover, admixtures of the present slag fabricatingmaterials and of the aforesaid scoria aggregates yield products ofintermediate physical properties. Also, scoria may be employed in one ormore layers of the composite structures while the slag may be used inothers, especially in the surface layers to enhance reflectivity,abrasion resistance, physical strength, etc.

More particularly, slag and slag-scoria mixture may be employed veryadvantageously in the fabrication of heavy duty traffic bearingsurfaces. In such fabrication the slag is employed in conjunction withcertain adhesive bonding agents to promote the bonding of a substratesurface to a variety of coating layers, the slag particles serving toprovide a mechanical interlock between the substrate, the bondingmaterial and the coatings, while the bonding agent is of a nature whichreacts with the coating material to practically fuse therewith. Theconcept is applicable not only in the provision of traffic surfaces butfor the application of successive constituent layers over metal, wood,brick and other surfaces of similar nature so as to provide a variety ofother composite mechanical structures. Moreover, the fragmented slagparticles produce a concave mirror effect because they have cup-shapedexterior surface depressions facing in all directions giving a uniformlyreflective surface. In addition to providing a remarkable degree ofbonding, the composite or lamellar structure produced as describedhereinafter, possesses other highly advantageous characteristics such asskid resistance, minimal ablation to fire, very high compressionstrength, shock resistance, and others.

Accordingly, it is an object of our invention to employ slag to promotethe bonding of various substrate surfaces to covering layers in thefabrication of composite and lamellar structures.

Another object is the provision of resinous bonding means to effect thesuccessful bonding of a layer of material such as an asphalticcomposition to a substrate of concrete or the like.

Another object of our invention is to employ slag in conjunction withresinous "bonding agents to promote the bonding of an asphaltic roadsurface covering to a substrate surface.

Still another object of our invention is to employ slag as a binding orcomponent layer over plane and curved surfaces in the fabrication oftraffic bearing surfaces or mechanical structures.

A further object of the invention is to employ slag in the fabricationof non skid traffic bearing surfaces incorporating a self-sharpeningeffect with surface usage.

A still further object is to produce a slag traffic bearing surface thathas a built in light reflective feature.

The invention possesses other objects and features of advantage, some ofwhich, with the foregoing, will be set forth in the followingdescription and the accompanying drawing of the preferred form of theinvention. It is to be understood, however, that variations in the formof the disclosed description and drawings may be adapted within thescope of the invention as set forth in the claims.

Referring to said drawing:

FIGURE 1 is a cross sectional view of a composite surface structure asapplied to a hard substrate surface in accordance with the invention.

FIGURE 2 is a cross sectional view of a composite surface structure asapplied to a soft unset substrate surface.

FIGURE 3 is an enlarged view of a portion of the structure whichdemonstrates the manner in which the light reflective feature of theinvention is incorporated therein.

FIGURE 4 is a cross sectional view of portions of a tubular compositestructure constructed in the process of the invention.

In brief, the fabrication processes of the invention generally involvean initial operation wherein a layer of slag particles or fragments isbonded to a relatively smooth substrate surface by means of certainadhesive agents. In this manner the substrate surface is covered by alarge number of relatively closely-spaced outwardly projecting slagfragments or particles tightly bonded thereto. Under certain conditionsapplication of a separate bonding agent may be dispensed with sincecertain substrates may be made to serve a similar purpose in earlystages of manufacture. The substrate surface prepared in this manner isnow in an ideal condition for the application of additional layers suchas of various paving or structural materials to complete the compositesurfaces and structures of the invention. Such additional layers may beof an adhesive character, however, it is not necessary that such be thecase since a firm mechanical bond will result between the slag andvarious dough-like materials which do not ordinarily otherwise yield asufiiciently strong bond.

In the fabrication of trafiic bearing surfaces in accordance with theinvention, the substrate on which the superimposed layers are appliedwill ordinarily be relatively rigid and unyielding such as set orhardened concrete as illustrated in FIGURE 1. Old or new concrete,asphaltic paving, wood, rock, brick, metal and other similar substancesare adaptable for the application of a composite surfacing in accordancewith the invention. A clean and roughened surface 11 is invariablynecessary to ensure the best result and, accordingly, loose material,oil and the like are removed by wire brushing, sweeping, sandblastingand other appropriate operations such as acid cleansing.

A layer 12 of fluid adhesive bonding agent is then applied as byspraying on the surface. The selection of an appropriate bonding agentwill depend on the nature of the substrate surface and the ambientconditions under which the surface is to be employed. In some instancesa solution of adhesive material which solidifies by evaporation of thesolvent, may be employed. Likewise, it is possible to employ bondingagents which can be applied in a molten condition and which solidify oncooling; however, it is generally preferred to employ a resinous bondingagent of the catalyzed setting type. Solvent solutions as asphaltic,coal tar or other resinous materials exemplify the first mentioned typeof adhesive bonding agents. Aqueous emulsions and dispersions ofadhesive bonding agents of a similar character may be employed likewise.Molten asphalts, coal tar, resins and synthetic resins exemplify thesecond type of bonding adhesive.

The preferred setting type of resin or chemically reactive class ofadhesive with which the maximum advantages of therslag particles areobtained constitute the catalyzed epoxy, phenolic, polystyrene, acrylicesters, resorcinol-formaldehyde, polyurethanes, polyester and siliconeresins which set at ordinary room temperatures and at accelerated rateswith increased temperatures. Epon resins (828 etc.) supplied by ShellChemical Company, Araldite resins (502,6010, 6020, etc.) supplied byCiba, Plastics Division, C-8, Devron and other epoxy resins aregenerally prepared by the condensation of epichlorohydrin and 'BisphenolA (4,4-isopropylidenediphenol) to various molecular weight polymersyielding viscosities of fluid, to molasses-like, to thermoplasticsolids. Catalysis by agents and mixtures thereof including organicbases, acid anhydrides, compounds containing active hydrogen, certainresins, and the like, is employed in the multitudinouscommercially-available formulations. Plasticizers such as Thiokol fluidand others can be employed therein. Phenolformaldehyde liquids can becured with organic bases, resorcinol-formaldehydes cure at roomtemperature with additional formaldehyde and urea-melamine-formaldehydecures at room temperature or coplymerizes with others of the phenolicand epoxies. True polymerizing adhesive bonding agents derived ofstyrene, allylic compounds, acrylic and methacrylic esters are curedwith benzoyl peroxide or other organic peroxide and especially in thepresence of a redox catalyst system. Polyurethanes and hybrids withpoly-urea cure in the presence of water and acid.

When the phenolic and especially, the epoxy type of adhesive bonding arecontacted with bituminous or asphaltic surfaces or compositions in thecourse of constructing the composite structures of the invention, achemical reaction has been observed to occur which markedly modifies theappearance of the asphalt or bitumen in the contact region. Microscopicexamination reveals that there is no sharply defined interface betweenthe resin and asphalt or bituminous phases of the bond region but that acoalescence occurs therebetween so that the intermediate region is ahighly modified resinasphalt or bitumen composition which varies toeither side of the intermediate region so as to attain the compositionof the adjacent phase. Although the nature of the reaction is not fullyunderstood, it is believed that a type of crosslinking reaction occursbetween the indicated types of resins and reactive sites of thecompounds in the asphaltic or bituminous materials. Active oxygen,hydroxyl, amine and other nitrogen substituents, and unsaturatedside-chains present in such materials would be susceptible of suchreaction. As a result the physical properties of the asphalt aremodified, e.g., the bond region is less thermoplastic than the adjacentasphalt, it is harder and more resistant to shock, tensile propertiesare improved, etc. It will therefore be apparent that the bond obtainedwith these materials is not merely the adhesion usually obtained bysurface effects but is literally a fusion to provide a far superiorinter-mingled bonding region. The intermingled bonding region producedby the composition of the above may be produced in volume thickness as ahomogenous mass as well as by creating a bonding contact layer. In otherwords, this composition of asphaltic tar epoxy resin and slag aggregatemay be a surface coating, or be of more extensive columetricproportions.

While the bonding agent layer 12 is still in a fluid state a layer ofthe slag particles 13, free of fines and uniform in size, is appliedwith rolling if necessary to assure that the lower surfaces thereof arethoroughly wet by the agent or are embedded partially therein. Withsurfaces such as walks, floors, decks, etc. to which only a relativelythin covering is to be applied, mesh sizes of A /8 inch or larger may beemployed. In the event that the surface is to be used by heavy vehiculartrafiic, or requires frictional characteristics materials of A1, /2 inchor larger mesh sizes are employed. Ordinarily, the bonding agent is thenallowed to set, heat being applied if necessary thereby conditioning thesubstrate surface for the bonding of additional layers of materialthereon. In this sense the bonding agent-slag layer will be understoodto constitute the bonding layer of the completed composite structure.

The covering or surfacing layer which may under certain conditions beconsidered a filler layer is applied over the layer 12, either in adough-like plastic or semiplastic state and rolled into the intersticesbetween the bonded aggregate fragments and into firm contact with resincovered substrate and aggregate surfaces or the ad ditional layers maybe built by applying dressings of the cinder-like aggregate and thenspraying a binder constituent thereover. Finally, a dusting layer ofaggregate particles of appropriate size may be applied or rolled, ifdesired, into the surface, particularly, where the maximum in non skidproperties is desired. For maximum adhesion of the dough-like layer 14,an adhesive bonding layer 15 is sprayed over the projecting fragments 13before layer 14 is applied.

For street and roadway surfacing or paving, e.g., reconditioning ofhighway surface, cold mix, hot paint mix and other types of asphaltic orcoal tar binding paving materials are employed as the layer 14.Alternatively, slag of a range of mesh sizes (dust to ca. 42 inch) maybe applied and an asphaltic emulsion or solution sprayed thereover, as abinder, similar to seal coat paving methods to provide layer 14.

With new concrete base roadways, the slag may be partially imbedded inthe soft concrete surface to provide the bonding layer as illustrated inFIGURE 2, thereby omiting the initial adhesive bonding layer ofFIGURE 1. In this case the completed surface structure will include aconcrete substrate 20 having a clean surface 21, slag fragments 22embedded therein and a covering layer 23 of dough-like fillercomposition bonded with adhesive layer 24 applied as by spraying on tothe upper substrate surface 21 and exposed surfaces of the slagfragments 22. In the event that filler 23 is sufficiently adhesive,bonding layer 24 may be omitted.

An enlarged view of the region of a single slag particle 22 partiallyexposed out of the covering layer 23 is shown in FIGURE 3 of the drawingto illustrate the manner in which the light reflective feature is builtin and also the manner in which the trafl'ic bearing surface is skidresistant.

As shown in FIGURE 3, the slag particle has many concave mirror effectsurfaces 25 facing all directions. This gives a uniform reflectivesurface for light proportional to the particle size and the number ofparticles per square foot as each particle summit is surrounded by avalley. In addition, the particle summits create a backward reflectiontowards the source rather than an angle reflection forward as will benoted by the majority of incident light rays 26 being reflectedsubstantially rearwardly from the surfaces 25 toward the light source.The cup-shaped exterior surfaces accomplish this either in daylight orat night time whether wet or dry.

The slag particles also maintain their very high and uniform coefiicientof frictional resistance with wear. When an exposed particle eventuallybreaks down and disintegrates an underlying particle thereby becomesexposed and also creates a non-skid surface. Thus, our inventionutilizes a uniformly frictional surface with a given number offrictional particles to the square foot. For example, one square foot ofslag or scoria surfacing composition registers between 15,000 to 20,000surface particles of /s" screen size per square foot. Thischaracteristic insures a consistently even vehicular braking actionsimultaneously on all wheels of each vehicle whether the surface is wetor dry.

In the event that a higher grade or structurally strong surface layer 14is required, e.g., in interiors, on decking, Walkways, rigid panels andthe like, it is preferred to employ a binder of the resinous adhesiveagent types described above. The amount of binder may be varied from theminimum required for cohesion and adhesion of the aggregate dressing tothe bonding layer to the amount necessary to provide an essentially nonporous surface.

Surfacings and coverings applied in the manner described are remarkablyadherent to the substrate surface. The bond is resistant to thermalshock and load bearing stresses as well as to weathering. With theamount of binder limited to increase the porosity, surface drainage isexcellent while, with increased amounts of hinder the layer as a wholeis water tight and therefore the substrate is protected to the maximumextent.

The principles described above are also employed in the fabrication ofstructural forms such as tubing, panels or for the application ofinsulation and corrosion resistant coverings to various surfaces. Forexample, very diflicult problems are encountered in providing corrosionresistant coverings for pipelines. A bonding layer of slag applied tothe substrate pipeline surface as described above facilitates theapplication of the conventional asphaltic and coal tar protectivecoverings. The bonding layer is particularly efficacious when a heatplasticized covering layer is extruded to cover pipeline sectionsprepared with the bonding layer as described above.

Tubing and panel sections as illustrated in FIGURE 4, are constructed byproviding a base 30 from metal,

fiber, sheet material, e.g., fiber glass matting or fibrous clothimpregnated with a fluid laminating resin of the epoxy, phenolaldehyde,polyester and similar types or with a thermoplastic binder as employedin conventional practice. While the binder or laminating resin is in afluid state the slag fragments 31 are applied as described above.Ordinarily, the binder is then allowed to cold set or the laminatingresin is at least partially cured with the application of heat ifnecessary to provide a stable layer of bonded aggregate fragments.

Subsequently, a plastic composition 32 of the aggregate in admixturewith an adhesive binder is applied smoothly over the bonding layer. Insome instances curing at this stage will produce a satisfactorystructure, however, for maximum strength an outer laminated coverlinglayer 33, similar to the substrate base is applied. Tubing or panelsections made in this manner are rigid, weather resistant, durable,light weight, economical and possess many other desirable properties.

Further details of the invention will be apparent in the followingexamples:

EXAMPLE I A substrate surface of hot asphalt plant mix applied over astandard crushed rock road base is covered with /2" screened slagaggregate of the character described above. While the substrate is stillin a heated condition the aggregate layer is rolled with suflicientpressure to imbed the aggregate particles about halfway into the softasphalt layer. The upwardly projecting portions of the particles nowpresent a large surface area including numerous spicules and concavitieswhile the lower portions are tightly imbedded in and bonded to theasphalt substrate.

A fluid setting adhesive agent is then applied as by spraying over theaggregate studded substrate surface. A suitable adhesive bonding agent Ais compounded, illustratively, a follows (various of the other adhesivesindicated may be used equivalently):

(1) Fluid resin (Applied Plastics Co., #210) parts 4-6 (2) Hardener(Applied Plastics Co., #180) part 1 (3) Plasticizer (General MillsCorp., #125) percent volume 3-10 A representative fluid epoxy resin typebonding agent B is prepared as follows:

Parts 1) Epon 828 (Shell Chemical Co.) (2) Triethenediamine orequivalent base 8 (3) Phenyl glycidyl ether (optional) 5 (4) FluidThiokol (plasticizer) 10 Application of the adhesive agent yields aprepared bonding surface on the aggregate studded substrate.

A dough-like aggregate preparation is applied over the prepared surfaceas by trowelling or with mechanical spreading equipment. The aggregatedough usually is prepared from slag aggregate of smaller screen sizesthan those comprising the bonding layer. An aggregate mixture C maycomprise, e.g., 1 part of A mix screened slag aggregate particles and 2to 16 parts of A2" screened particle sizes. The aggregate mixture C isadmixed with 5 to 20% by volume of either mixture A or B determined bythe amount of interstitial porosity which is desired in the finishedsurface. The larger proportion of resin is suflicient to provide anessentially smooth surface, if desired.

The aggregate dough is applied in a thickness which is at leastsufiicient to cover the bonding aggregate par ticles (about A") andgenerally in depths to at most of about 1" in thickness. A maximuminitial frictional surfacing is obtained by dusting the surface withaggregate fines. Dependent on the temperature the surfacing hardens intimes ranging from less than an hour at elevated temperatures to severalhours at usual ambient temperatures.

The surfacing obtained in this manner is harder, more wear resistant andskid resistant than ordinary asphalt surfacings. The asphalt isprotected by the insulative qualities of the aggregate from buckling,rolling and cracking under variant temperatures and pressures andrepairs may be quickly made by replacing damaged surface in the samemanner as the surfacing i usually applied to the aggregate bondinglayer. The surface may be the naturally-attractive color of theaggregate or pigmented aggregate may be employed in providing the finalsurfacing. Moreover, the surfacing is inseparable from the substratesurface and is very resistant to damage from thermal shock.

Old asphalt or bituminous surfaces are treated in a similar fashion;however, the old surface is cleaned and degreased or abraded and acoating of mixture A or B is sprayed thereon prior to application of thebonding aggregate particles. A very firm bond is thereby obtained to theold surface.

EXAMPLE II A substrate of freshly poured and rough finished concrete isan ideal base for applying a surfacing in accordance with the invention.Before the concrete has set, a layer of the slag aggregate of V2 to 1"screen size is spread evenly over the surface and rolled to imbed theparticles about halfway into the concrete. After the concrete has set alight coating of mixture A or B of Example I is sprayed over theappregate bonding layer and dough-like mixture C of Example I is spreador trowelled smoothly into place. Curing takes place as in Example I.

The surfacing applied over concrete as described herein has essentiallythe same advantageous properties as those described in Example I.However, certain additional advantages are also obtained, viz., thesurfacing eliminates the dusting of the concrete substrate and ifapplied within a few days after the concrete is poured, curing of theconcrete is promoted through moisture retention. Old concrete traffichearing or wall surfaces are resurfaced in the same manner; however, inthis case the surface is sandblasted or abraded mechanically or acid isapplied thereto to remove dirt and oxidized materials whereby anadequate aggregate bond is obtained.

EXAMPLE III Rigid or semi-rigid plastic materials such as panels orother forms of foamed polyethylene, isocyanate, polystyrene or phenolicresins are also suitable substrates. Very often such foamed materialsare employed in walls, roofing and floors of refrigeration, or marineinstallations wherein heavy loads or traffic is encountered.

To apply the aggregate bonding layer an adhesive coating of hot tar orof an asphaltic adhesive cement is applied to the load bearing surface.While the adhesive is still soft slag aggregate particles of from A to/2" screen size is imbedded therein and the adhesive is allowed toharden. Finally, the aggregate surfacing is applied as described inExample I.

It will be appreciated that the surfacing is applicable to panels priorto installation or in situ. The surfacing enhances the insulative value,fire resistance and water absorption characteristics of the foamed resinmaterial. If the treated panels are to be employed for visible surfaces,the appearance can be modified by scrolling, texturing or application ofpigmented aggregate material. In some cases, where water resistance isnot critical, the adhesive tar mixture may be eliminated and thedoughlike mixture spread and rolled to effect the bond either with orwithout the application of bonding adhesive agent such as A or B.

EXAMPLE IV A metal substrate surface is cleaned by degreasing or otherappropriate means such as sand blasting or wire brushing. A catalyzedsetting adhesive resin of the phenolic, epoxy or silicone type having aheavy molasseslike consistency, e.g., 1000 to 5000 centipoises isapplied as a coating to the metal substrate surface. Slag aggregateparticles in uniform sizes preferably in the range of A to about /2"mesh size are then applied to the surface as a uniform layer and theresin is caused to set, with moderate heating, if necessary, to providean aggregate bonding layer.

The final surfacing which is applied thereover will be determinedprimarily by the application in which the surfacing is employed. Marinedecking and trafiic bearing decking such as bridges, etc., are providedby applying a dough-like, resin-aggregate mixture similar to that ofExample I and in a similar manner.

Steel and iron pipeline substrate surfaces may be prepared in a similarmanner. However, for this and similar applications, lower cost materialshave been found to yield satisfactory results. Under conditions in whichsevere soil stresses are encountered, the aggregate bonding layer isapplied as above. Subsequently, a thermoplastic bituminous mixturecomposed of slag aggregate mixture C and about 20 to 35% of asphalt orcoal tar having a melting point of at least 50 C. is heated and extrudedaround the aggregate studded pipeline sections with conventionalmachinery. Surfacing layers of /2 to 2 or more inches thickness areapplicable in this fashion. The aggregate being firmly bonded to themetal by the resin and the extruded material being firmly bonded to theoutwardly projecting aggregate portions results in a very stronglyadherent bituminous coating on cooling.

Under some conditions a heated coal tar adhesive may be employed as theadhesive employed to bond the aggregate particles to the pipelinesurface. Also an outer layer of coal tar or asphalt pipe enamel with orwithout the conventional outer wrapping may also be employed,especially, in splicing or repairing.

A coating applied in this manner is not only exceptionally adherent anddurable but is also water proof, insulative, and eliminates oxidative,chemical or galvanic corrosion.

EXAMPLE V Load bearing panel-like structures having high stiffness toweight ratios are prepared in the following manner;

A lower sheath substrate comprising either a thin sheet of light metalsuch as aluminum or one or more layers of glass cloth are coated orsaturated with a catalyzed epoxy or phenolic contact laminating resinand is disposed in a horizontal position. A layer of the slag aggregateof a closely graded screen size approximating the thickness of thefinished sheet is spread uniformly over the resin coated surface. Tofacilitate handling the resin is at least partially set by heating and alight coating of the laminating resin is sprayed over the upwardlyprojecting aggregate particles.

A dough-like filler prepared by mixing van'ous proportions of aggregatefines and screen sizes smaller than the interstices between the bondedaggregate particles (cf. Example I) 10 to 25 parts of the catalyzedlaminating resin is then spread to fill the interstices of the bondedaggregate particles.

Finally an upper substrate sheath similar to the lower is coated with alight layer of the resin and pressed into contact with the upper surfaceof the bonded filler layer and the complete structure is allowed to curewith the application of heat. Curing between platens with a moderatepressure (5 to 50 lbs. per square inch) yields a more compact, rigid anddimensionally accurate structure.

EXAMPLE VI A tubular structure such as a cylindrical section or a tubehaving a high rigidity to weight ratio is manufactured as follows:

A fiber glass fabric or matting is saturated with a thermosetting epoxyor phenolic adhesive laminating resin and wound around a collapsiblemandrel in one or more layers to provide a cylindrical substratesurface. Then an aggregate bonding layer of screened slag aggregateparticles, of a uniform to 1 inch mesh size, is partially imbedded inthe resin coated substrate and the resin is at least partially cured toprovide an aggregate studded cylindrical substrate which can be handled.

The cylindrical substrate is removed from the mandrel and a lightcoating of the laminating adhesive is sprayed over the aggregatesurface. Then a dough-like layer of slag aggregate fines and particlesizes smaller than the bonded aggregate prepared as described above isapplied over the aggregate studded cylindrical substrate, preferably byextrusion.

The assembly produced as described above may be cured to produce tubessuitable for many purposes. For example, the ends of the tubes can betapered and connected by collars to provide pipe-lines, etc.; however,for maximum rigidity at least one external layer of resin saturatedglass fiber fabric is wrapped spirally around the assembly and thecomplete assembly is cured with heating if required.

What is claimed is:

1. In a process for fabricating a composite structural surface, thesteps comprising applying to a substrate surface a setting fluidresinous material selected from a group consisting of epoxy, polyester,phenolic, acrylic, polystyrene, polyurethane and silicones, applying andpartially embedding a layer of slag particles in said resinous materialwhile it is in its fluid state, said slag particles being particles of aslag material containing metal oxides and produced as a dross ofsmelting a metal from an ore containing silicates, and applying a fillerlayer of a composition including an aggregate in admixture with a binderto said surface, whereby the layer of slag particles serves as a bondinglayer for the additional layer of composition.

2. A composite structure comprising a substrate base, a layer ofresinous material selected from the group con sisting of epoxy,polyester, phenolic, acrylic, polystyrene, polyurethane and siliconesbonded to said base, a layer of coarse slag particles partially embeddedin said layer of resinous material, said slag aggregate particles beingparticles of a slag material containing metal oxides and produced as adross of smelting a metal from an ore containing silicates, and a fillercomposition of slag aggregate and adhesive binder bonded to said layerof aggregate particles with some of said slag particles protruding fromsaid filler composition to provide concave mirror light reflectivecharacteristics and a high coefiicient of frictional resistance to thesurface of said structure.

3. In a process for fabricating a composite structural surface, thesteps comprising applying to a substrate surface a setting fluid epoxyresin, applying and partially embedding a layer of slag particles insaid epoxy resin while it is in its fluid state, said slag particlesbeing particles of a slag material containing metal oxides and producedas a dross of smelting a metal from an ore containing silicates, andapplying a filler layer of a composition including an aggregate inadmixture with a binder to said surface, whereby the layer of slagparticles serves as a bonding layer for the additional layer ofcomposition.

References Cited UNITED STATES PATENTS 2,158,772 5/1939 Beckwith 156-2802,306,295 12/1942 Casto 156-278 2,963,045 12/1960 Canevari et al.138-146 3,008,493 11/1961 Roe 138-146 3,033,088 5/1962 Wittenwyler 94-223,161,114 12/1964 Wittenwyler 94-22 2,925,831 2/1960 Welty et al. 94-222,934,452 4/1960 Sternberg.

3,038,393 6/1962 Nagin 94-9 JACOB L. NACKENOFF, Primary Examiner.

1. IN A PROCESS FOR FABRICATING A COMPOSITE STRUCTURAL SURFACE, THESTEPS COMPRISING APPLYING TO A SUBSTRATE SURFACE A SETTING FLUIDRESINOUS MATERIAL SELECTED FROM A GROUP CONSISTING OF EPOXY, POLYESTER,PHENOLIC, ACRYLIC POLYSTYRENE, POLYURETHANE AND SILICONES, APPLYING ANDPARTIALLY EMBEDDING A LAYER OF SLAG PARTICLES IN SAID RESINOUS MATERIALWHILE IT IS IN ITS FLUID STATE, SAID SLAG PARTICLES BEING PARTICLES OF ASLAG MATERIAL CONTAINING METAL OXIDES AND PRODUCD AS A DROSS OF SMELTINGA METAL FROM AN ORE CONTAINING SILICATES, AND APPLYING A FILLER LAYER OFA COMPOSITION INCLUDING AN AGGREGATE IN ADMIXTURE WITH A BINDER TO SAIDSURFACE, WHEREBY THE LAYER OF SLAG PARTICLES SERVES AS A BONDING LAYERFOR THE ADDITIONAL LAYER OF COMPOSITION.